This application claims the priority of German application DE 198 19 713.6 filed in Germany on May 2, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a steering column for a motor vehicle with a steering shaft rotatably mounted in a jacket tube, with the jacket tube having at least one deformation element associated therewith, said deformation element being plastically deformable with energy absorption during axial displacement of the jacket tube.
A steering column of the above described general type is known from German Published Unexamined Patent Application No. DE 28 21 707 A1, said column being connected with the body by a deformation element. The deformation element is in the form of a U-shaped energy-absorbing metal strip. A free end of one leg is connected with the steering column and the free end of the other leg is connected with the body. In addition, the metal strip is housed in a box in which the legs of the strip abut opposite sides of the box. When the steering column is displaced axially relative to the body, the metal strip is subjected to so-called rolling bending defined by the position of the strip in the box.
A steering column of the above described general type is also known from German Patent No. DE 195 42 491 A1, said column having an axially displaceable jacket tube supported integrally on the body by an energy-absorbing deformation member. A bent metal band is provided as the deformation member, said band being connected permanently at one end with the jacket tube and at the other end with the body. The metal band is also accommodated in a guide in which it is deformable either by linear displacement or by rolling bending.
A steering column for a motor vehicle is known from German Published Examined Application DT 16 30 882 B2, said column comprising a jacket tube for a steering shaft inserted into a sleeve-shaped receptacle integral with the vehicle. A rigid shaping tool is also mounted on the receptacle. This tool plastically deforms the jacket tube with energy absorption during axial displacement of the jacket tube relative to the receptacle. In a modified embodiment, the shaping tool is mounted on the jacket tube and upon an axial displacement of the jacket tube, deforms the receptacle on which the jacket tube is mounted, including the shaping tool.
A goal of the invention is to provide a steering column of the type recited at the outset that exhibits improved deformation behavior.
This goal is achieved according to the invention by the fact that the (at least one) deformation element is secured at least unilaterally to the jacket tube and abuts deflection structure mounted on the body, said deflection structure being positioned axially with respect to the deformation element in such fashion that the deformation element is deformed by the deflecting structure when the jacket tube is displaced axially. The deformation element together with the jacket tube is moved past the deflecting structure, resulting in a deliberate and very precisely calculable deformation of the deformation element. The arrangement of the deflecting structure integrally with the body, and hence integrally with the vehicle, also ensures a specific axial displacement of the jacket tube.
In certain preferred embodiments of the invention, the deflecting structure has at least a first rigid deflecting element and at least a second deflecting element associated therewith that fit around the at least one deformation element. As a result, the deformation element is guided and positioned exactly.
In certain preferred embodiments of the invention, the first deflecting element and/or second deflecting element are in flush contact with the deformation element. When the deformation element moves relative to the deflecting elements, frictional work can be done deliberately, absorbing additional energy.
In another embodiment of the invention, the deformation element is in the form of an elongate flat element. In this manner, the entire arrangement can be produced in a manner that saves both space and weight.
In certain preferred embodiments of the invention, the deformation element is subjected to continuous plastic deformation during an axial displacement of the jacket tube. The deformation element is deformed in a spatially limited way, with the deformation propagating like a wave through the deformation element from the standpoint of the deformation element. Since the deformation element is deformed twice at every point through which the deformation passes, firstly from a non-deformed state into a deformed state and secondly back again into the initial state, an especially high degree of deformation results and hence the arrangement has a large energy absorption capacity.
In certain preferred embodiments of the invention, the deformation element is subjected to rolling bending during axial displacement. The rolling bending constitutes a special case of plastic deformation that passes through the deformation element. The deformation element is unrolled on the relative surface and likewise continuously deformed. Rolling bending can be performed deliberately and in a manner that can be determined in advance with the aid of the deflecting structure mounted on the body.
In certain preferred embodiments of the invention, the deformation element is forcibly guided between a first deflecting element in the form of a mount that is aligned transversely to the displacement direction of the jacket tube and a second deflecting element in the form of an opposite mount. Preferably, the mount is located offset with respect to both the opposite mount and to the fastening point of a deformation element on the jacket tube, axially opposite the displacement direction of the jacket tube. In this manner, high contact forces between the deformation element and a mount can be produced by displacing the jacket tube.
In certain preferred embodiments of the invention, the deformation element is forcibly guided between a first deflecting element in the form of a mount that is made wedge-shaped in the displacement direction of the jacket 2 and the second deflection element in the form of an opposite mount. With the aid of the wedge-shaped mount, the deformation element can deflect from its initial position with plastic deformation during displacement of the jacket tube. The opposite mount then serves as an additional guide.
In certain preferred embodiments of the invention, a guide gap is formed between the mount and the opposite mount that is aligned at an angle to the displacement direction of the jacket tube. Depending on the alignment and dimensioning of the guide gap, larger or smaller frictional forces can be produced between the mount and the opposite mount on the one hand and the deformation element on the other hand.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.